P300 BCI: Reading the Mind

Alice Bosma-Moody -

We tend to take communication for granted. Talking, laughing, smiling, and writing are integral components of our lives. And while we overlook their presence, their absence has profound impacts. For patients with severe motor disabilities, such as locked-in syndrome or Amyotrophic Lateral Sclerosis (ALS), the ability to control the fine motor movements of speech is lost, but consciousness often remains [1]. Communication is an obvious component of a healthy and independent lifestyle for these patients.  

The P300 is an early Brain-Computer Interface (BCI) that takes advantage of the brain’s natural electrical response to visual stimuli. The brain’s electrical activity can be noninvasively recorded with Electroencephalographic (EEG) techniques via electrodes placed on the head. In the earliest P300 BCIs described, the 26 letters of the alphabet and digits 0-9 were arranged in a 6 by 6 grid on a screen [2]. The P300 BCI operates on the principles of the Oddball Paradigm. When a subject is engaged in the task, the individual will note the number of unique, target events – the “oddballs” – in a series of normal, non-target events [1]. This noting of an “oddball” reliably produces a positive deflection in brain activity in the parietal cortex with a roughly 300 millisecond delay following the event. When the P300 BCI is applied, the user counts the number of times the desired letter or number flashes on the screen flashes [2]. The computer repeatedly flashes different rows and columns until the decoding algorithm can assign the EEG recorded evoked potentials to a specific target. While this may seem like a slow way to select a single letter or number, the implementation of word completion software and the relative ease of use have led to a positive reception of the P300 BCI in the community.

The initial description of the P300 BCI in 1988 by Farwell and Dochin was initially overlooked [1]. Researchers, however, began to take note in the late 1990s and early 2000s and improve upon the previously described paradigm. More recently, researchers have found ways to reduce complexity and cumbersome hardware support to make at-home use feasible and reliable [3]. Furthermore, some groups have created novel software programs for internet browsing, painting, and gaming [1]. Although not as fast as texting or as easy as talking, the P300 and its recent improvements serve the important function of providing a means of communication for individuals impacted by a wide range of disabling conditions.

References

  1. Fazel-Rezai, Reza et al. “P300 Brain Computer Interface: Current Challenges and Emerging Trends.” Frontiers in Neuroengineering 5 (2012): n. pag. PubMed Central. Web. 18 Aug. 2015.
  2. Farwell, L. A., and E. Donchin. “Talking off the Top of Your Head: Toward a Mental Prosthesis Utilizing Event-Related Brain Potentials.” Electroencephalography and Clinical Neurophysiology 70.6 (1988): 510–523. Print.
  3. Vaughan, Theresa M. et al. “The Wadsworth BCI Research and Development Program: At Home with BCI.” IEEE transactions on neural systems and rehabilitation engineering: a publication of the IEEE Engineering in Medicine and Biology Society 14.2 (2006): 229–233. PubMed. Web.